The subject of photoperiodism concerns the influence of light and dark periods in the daily cycles of 24 hours on the living processes in plants. Photoperiod refers to the duration, i.e., length of the time of exposure to light, in other words, illumination period in daily cycle of 24 hours. Generally speaking photoperiodic response refers to any morphological, anatomical or physiological response produced in a plant by exposure to some particular photoperiodic cycles (e.g., periods of darkness). Flowering is one of such photoperiodic responses that plants may exhibit. It is important to note, however, that photoperiodic response in a photoperiodically sensitive plant is largely dependent on the duration of darkness experienced by the plant during a 24 hour cycle.
In particular, qualitative (i.e., obligate) short-day plants are such plants that necessarily flower as nights (i.e., dark periods) exceed a certain critical length. In nature this happens when days become shorter as the seasons develop and the year progresses towards the end, especially when the plants grow outside of the equatorial belt (within which the days and nights are of approximately the same duration and the night length does not vary much). On the contrary, long-day and especially qualitative (i.e., obligate) long-day plants will flower only when the nights are shorter than a certain critical length.
An irrigation rig is a device employed in irrigation or farming whereby the device provides plants and crops with water via sprinklers. The irrigation rig may automatically move from a first location to a second location while watering the plants and crops as the irrigation rig moves.